Oscillator controlled electronic ignition system



Jan. 28, 196 9 o, SEN ET AL v 3,424,142-" OSCILLATOR CONTROLLED ELECTRONIC IGNITION SYSTEM Filed Nov. 9, 1966 Sheet 0:2

' RNQKS Jan. 28, 1969 o, K, NlLsSEN ET AL 3,424,142

OSCILLATOR CONTROLLEDELECTRONIC IGNITION SYSTEM Filed Nov. 9, 1966 Sheet 2 of 2 F/GJ i I 70 Q .501 a0 5 78 LA F/Gi OLE KN/LSSEN JOSEPH F Z/OMEK INVENTORS' United States Patent 8 Claims ABSTRACT OF THE DISCLOSURE The amplifying transistor of a blocking type oscillator is connected in series with the ignition coil primary winding and a capacitor capable of absorbing substantially all variations in current during oscillation is connected in parallel with the transistor so the oscillator produces a unidirectional current in the coil primary winding during oscillation. When the oscillator switches to quiescence, the current in the coil primary winding drops precipitously to a negligible amount and thereby induces energy in the coil secondary winding to produce an ignition pulse. An additional inductor is included in the transistor output circuit to assist in precipitously turning off the oscillator.

This invention provides an electronic ignition system for an internal combustion engine that uses the change in current through an oscillator between oscillation and quiescence to produce an ignition pulse. A single ignition pulse is produced for each ignition cycle so spark plug life is increased significantly over other oscillator ignition systems.

In prior oscillator ignition systems, the oscllations themselves appeared in the coil primary winding and were induced into the coil secondary winding. The resultant oscillating voltage at the spark plug terminals produced several spark discharges for each ignition cycle. While some earlier engines may have required multiple discharges per cycle to achieve proper combustion, present day engines have been sophisticated sutficiently to obviate all but a single discharge per cycle. The multiple discharges increased erosion of the spark plugs and the distributor contacts and produced serious high frequency shielding problems. Nevertheless, oscillator controlled ignition systems remained desirable because of the adaptability of light weight breakerless mechanisms for control purposes.

By producing a single ignition pulse per cycle, the oscillator controlled ignition system of this invention retains the advantages of the oscillator systems while avoiding the disadvantages. In this system, an oscillator switchable from an oscillating state to a quiescent state produces a unidirectional current in the coil primary during oscillation, and negligible current during quiescence. During the change from oscillation to quiescence, the energy stored in the coil primary is induced into the coil secondary to produce an ignition pulse. A breakerless mechanism made of a diamagnetic material rotating through a feedback transformer in timed relationship to the engine can be used to turn the oscillator from oscillation to quiescence precipitously, thereby utilizing the stored energy with a high degree of efliciency.

An amplifying circuit can be used between the oscillator and the coil primary to produce the necessary energy level. With proper selection of components, the oscillator produces current changes sufiiciently large to induce a secondary voltage capable of firing an ignition plug directly. The oscillator then is connected in series with the coil primary winding. Details of construction and operation along with other advantages provided by the ignition sys- 3,424,142 Patented Jan. 28, 1969 tern of this invention are presented below in connection with the drawings in which:

FIGURE 1 is a schematic diagram of an ignition system of this invention in which the oscillator controls current through the col primary winding without further amplification;

FIGURE 2 in a schematic diagram of an ignition system in which an amplifier circuit couples the oscillator to the coil primary winding;

FIGURE 3 is a perspective view showing the mechanical structure of a breakerless mechanism used to turn the oscillator from oscillation to quiescence that comprises a diamagnetic vane rotating through a gap in a feedback transformer; and

FIGURE 4 is a cross-sectional view taken along line 44 of FIGURE 3 showing additional structural details of the rotating vane and the transformer.

CONSTRUCTION OF FIGURE 1 A battery serving as the source of energy is represented generally by the numeral 10 in FIGURE 1. Battery 10 has a positive terminal 12 connected through an ignition switch 14 to a positive buss lead 16. The negative terminal 18 of battery 10 is connected to a negative buss lead 20 and to ground at 22. A typical battery 10- produces a no load potential of about 12 volts.

An ignition coil 24 having a primary winding 26 and a secondary winding 28 has one side of secondary winding 28 connected to ground at 30. The other side of secondary winding 28 is connected through lead 32 to the rotating arm 34 of a distributor assembly 36. Arm 34 sequentially connects one of a plurality of spark plugs 38 to lead 32.

An electronic oscillator of the blocking type is enclosed by dotted line 40 and comprises a feedback transformer 41 and a transistor 44. Transformer 41 has a substantially circular core 42 that is split by a small air gap 43. A primary winding 48 and a secondary winding 50 are wound on core 42.

One side of coil primary winding 26 is connected through a resistor 52 to lead 16 and the other side is connected by a lead 54 to the dotted terminal of winding 48. The undotted terminal of winding 48 is connected to the collector 44c of transistor 44. Emitter 44e of transistor 44 connects with resistor 56 that in turn is connected through an inductor 60 to lead 20. A capacitor 63 is connected between lead 54 and lead 20 in parallel with winding 48, collector 44c, emitter 44e, resistor 56, and inductor 60'.

Transformer secondary winding 50 has its dotted terminal connected to the base 44b of transistor 44. The undotted terminal of winding 50 is connected through a resistor 62 to lead 16 and to the anode 64a of a diode 64 that has its cathode 640 connected to lead 20. Diode 64 preferably has a relatively long storage time so it will constitute a low AC impedance from secondary winding 50 to lead 20.

A timing device 66 comprises a cup-shaped vane 68 mounted on a shaft 70. Shaft 70 is driven in a conventional manner, usually from the engine camshaft (not shown). The web 72 of vane 68 comprises a plurality of cutouts 74, only one of which is shown in FIGURE 1, and is adapted to move through gap 43. Web 72 preferably is m-ade of a diamagnetic material such as brass. Dotted line 76 represents a mechanical connection between shaft 70 and arm 34.

CONSTRUCTION OF FIGURES 3 AND 4 As shown FIGURES 3 and 4, vane 68 rotates in a bowl-shaped housing 7-8. Transformer 41 is mounted on a plate located near the floor of housing 78 in a position where web 72 passes through gap. 43. The top of shaft 70 has a space for arm 34 of distributor assembly 36. A conventional spark advance means 82- can be associated with plate 80, if desired. Transformer core 42 is made of ferrite and is mounted in a conducting shield 84. Plate 80 can comprise a printed circuit board and the other components of the circuit can be mounted on the board within housing 78.

OPERATION OF FIGURE 1 Windings 48 and 50 are arranged on core 42 so current into a dotted terminal of a winding induces current going out of the dotted terminal of the other winding.

Transistor 44 is of the NPN type, a typical useful transistor being Delco DTS 423, having'a rating of 400 volts, 3.5 amperes continuous and amperes peak current. When ignition switch 14 is turned on, positive voltage is applied through resistor 52, winding 26, and winding 48 to collector 44c of transistor 44. Positive voltage also is applied through resistor 62 and winding 50 to base 44b. Resistor 52 typically is about 3 ohms and resistor 62 typically is about 500 ohms. Diode 64 biases transistor 44 slightly into conduction, but the bias is insufficient to sustain oscillation when the diamagnetic material of Web 72 is in gap 43. Such a slight forward bias is desirable because it permits transistor 44 to break rapidly into conduction when the bias is increased. A typical useful diode 64 is No. 1N4001.

When a cutout 74 is in gap 43, sufiicient feedback occurs from winding 48 to winding 50 to induce an additional increment of voltage at base 4411. Typically, gap 43 is about 0.055 inch, winding 48 is 10 turns of 20AWG wire, and winding 50 is 12 turns of 20AWG wire. The additional increment of voltage increases the bias on base 44b sufficiently so transistor 44 begins conducting. As conduction begins, current through winding 48 increases and in turn increases the induced voltage at base 44b to increase the conduction of transistor 44. Transistor 44 continues to increase its conduction until it saturates.

At saturation, the increase in current through winding 48 stops and the induced increment of voltage at base 44b disappears. Base 44b then becomes negative with respect to emitter 44e and current through transistor 44 falls rapidly to a very low value.

The decreasing current through winding 48 induces a negative voltage at base 44b that keeps transistor 44 off until the negative voltage is dissipated through resistor 62. At this point, conduction of transistor 44 begins again and the above cycle is repeated in an oscillatory manner as long as a cutout 74 is in gap 43. Oscillation frequency is determined primarily by the inductance of winding 48 and is at least several kilocycles per second, preferably ranging above several megacycles per second. During oscillation, when current through transistor 44 falls, current through coil primary winding 26 passes into capacitor 63 which is selected so the current through coil primary '26 is constant. A typical value for capacitor 63 is 0.25 microfarad at 400 volts.

Vane 68 is made of a diamagnetic material such as brass. As vane 68 moves into gap 43, the gain of transformer 41 is reduced until the voltage induced in winding 50 falls below the level necessary to sustain oscillation. The presence of vane 68 in gap 43 also decreases the self-inductance of winding 48, thereby increasing the oscillation frequency of oscillator 40. This increased frequency in turn increases the reactance of inductor 60 which typically is about 0.05 microhenry, thereby increas ing the impedance provided by inductor 60. Preferably, transistor 44 is selected so its gain decreases significantly with the increase in frequency resulting from the change in self-inductance of winding 48.

The decreasing gain of transformer 41 and transistor 44 plus the increased impedance oifered by inductor 60 operate in cascade to stop oscillation precipitously. Current through coil primary winding 26 falls abruptly, thereby inducing a secondary YOltage in secondary Winding 28.

The secondary voltage is applied to an appropriate spark plug 38 by distributor assembly 36. Subsequently, another cutout 74 moves into gap 43 and oscillation resumes. The current through coil primary Winding 26 is substantially a square wave, rising somewhat slowly to a steady state value at the beginning of oscillation and falling precipitously when oscillator 40 becomes quiescent.

If desired, a capacitor can be connected in parallel with diode 64 to decrease further the AC impedance between secondary Winding 50 and ground 22. Vane 68 can have a planar or other shape and can be made of a ferromagnetic or paramagnetic material. Oscillator 40 can be designed so no oscillation takes place when a cutout 74 is in gap 43, and movement of web 72 into gap 46 begins oscillation.

CONSTRUCTION OF FIGURE 2 Numerals introduced in FIGURE 1 designate the same components in FIGURE 2. The construction of oscillator 40 is the same except a resistor replaces coil primary winding 26. Lead 54 connects resistor 110 to the dotted terminal of Winding 48 and capacitor 63.

A resistor 112 connects lead 54 with the base 1161) of a transistor 116. Transistor 116 is of the PNP type. Collector 1160 is connected through a resistor 120 to lead 20. Emitter 1166 is connected through a resistance 126 and a lead 128 to the base of a transistor 130.

Transistor 130 also is of the PNP type. A lead 132 connects emitter 1302 through a resistor 134 to buss lead 16. A resistor 136 is connected between leads 128 and 132 and a capacitor 138 is connected between leads 20 and 132. a

A lead 140 connects collector 130C to a resistor 142 that is connected to the primary winding 26 of ignition coil 24. The other terminal of Winding 26 is connected to buss lead 20. A Zener diode 144 has its anode 144a connected to lead 140 and its cathode 1440 connected to lead 132.

OPERATION OF FIGURE 2 When oscillator 40 is oscillating, the voltage in lead 54 is low. The voltage at base 116b then is less than emitter 116:: but greater than collector 1160 so transistor 116 is turned on. Base 1301; also has a voltage thereon less than emitter 130e but greater than collector 1300 so transistor 130 is conducting and a current exists in coil primary 26.

As oscillator 40 switches precipitously to quiescence, current through resistor 110 drops rapidly to zero. The voltage increase in lead 54 is applied through resistor 112 to base 116b to turn off resistor 116. Voltage at base 130k also rises to turn off transistor 130, thereby collapsing the field in coil 24 to induce an ignition voltage in coil secondary winding 28.

Thus, this invention provides an oscillator controlled ignition system that applies a single ignition pulse per ignition cycle to the spark plugs. A service-free breakerless mechanism switches the oscillator between its two states of oscillation and quiescence. When the breakerless mechanism uses a diamagnetic material to control feedback through a transformer, it combines with transistor characteristics and an inductance in the transistor output circuit to switch precipitously from oscillation to quiescence, thereby utilizing the energy stored in the coil primary winding with a high degree of efliciency.

What is claimed is:

1. An ignition system for an internal combustion engine comprising a source of electrical energy,

an ignition coil with primary and secondary windings,

and

an electronic oscillator switchable from an oscillating state to a quiescent state, said oscillator producing a unidirectional current in the coil primary Winding to store energy therein during one state and inducing that energy into the coil secondary winding when changing to the other state, the amplifying means of said oscillator being in series with the coil primary winding.

2. The ignition system of claim 1 in which the oscillator comprises a transistor having an input circuit and an output circuit,

a feedback means providing a feedback path from said output circuit to said input circuit, and

timed means rotated by the engine for interrupting the feedback path in timed relationship to the engine to switch the oscillator to a quiescent state.

3. The ignition system of claim 2 in which the feedback means comprises a magnetic circuit and the timed means comprises a rotating vane interrupting said magnetic circuit.

4. The ignition system of claim 3 in which the magnetic circuit comprises a transformer having a gap therein, and the vane has cutout portions rotatable through the gap in said transformer, said vane being made of a diamagnetic material.

5. The ignition system of claim 4 in which the oscillator is a blocking oscillator.

6. The ignition system of claim 5 in which the output circuit of the transistor contains an inductor means.

7. An ignition system for an internal combustion engine comprising a source of electrical energy,

an ignition coil with primary and secondary windings,

and

a blocking type electronic oscillator switchable from an oscillating state to a quiescent state, said oscillator producing a unidirectional current in the coil primary winding to store energy therein during one state and inducing that energy into the coil secondary Winding when changing to the other state, said oscillator comprising a transistor having an input circuit and an output circuit,

said output circuit containing an inductor means,

a feedback means including a magnetic circuit providing a feedback path from said output circuit to said input circuit, said magnetic circuit including a transformer having a gap therein.

timed means including a vane rotated by the engine for interrupting the magnetic circuit in timed relationship to the engine to switch the oscillator to a quiescent state, said vane being made of a diamagnetic material and having cutout portions rotatable through said gap in said transformer, and

a capacitor connected in parallel with the transistor, said capacitor absorbing substantially all variations in current through the transistor during oscillation.

8. The ignition system of claim 7 in which the oscillator is in series with the coil primary.

References Cited UNITED STATES PATENTS 3,209,739 10/1965 Jukes 123148 3,277,340 10/1966 Jukes et al l23l48 LAURENCE M. GOODRIDGE, Primary Examiner.

U.S. Cl. X.R. 315209 

